Which of the following pairs will give displacement reactions?

Correct answer: (a) AgNO3 solution and copper metal

Explanation

In a displacement reaction, a more reactive metal displaces a less reactive metal from its salt solution.

Copper is more reactive than silver, so Cu displaces Ag: Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag; solution turns blue, shiny silver deposits.

The other pairs fail – Cu cannot displace Na, and Ag and Al are less reactive than Fe and Mg respectively.